The present invention relates to an apparatus for controlling a charging generator, and more particularly to a charging generator control apparatus having a switch device and a diagnostic device for detecting and indicating malfunctions or failures of the charging generator. The present application is related as to subject matter to U.S. Ser. Nos. 477,802 and 478,126, by the present inventor.
One conventional apparatus for controlling a charging generator is shown in FIG. 1 of the accompanying drawings. A three-phase a.c. generator 1 is installed on an auto (not shown) and is drivable by the engine thereof (not shown). The generator 1 has three-phase star-connected armature coils 101 and a field coil 102. The a.c. output from the generator 1 is rectified by a full-wave rectifier 2 having a first rectifier output terminal 201, a second rectifier output terminal 202, and a ground terminal 203. A voltage regulator 3 serves to control the output voltages from the generator 1 so as to obtain a first preset value by controlling the field current flowing through the field coil 102.
The voltage regulator 3 comprises a surge absorber diode 301 connected across the field coil 102, a pair of Darlington-connected power transistors 302, 303 for turning the current passing through the field coil 102 on and off, a resistor 304 connected to the base of the transistor 303, a control transistor 305 for turning the transistors 302, 303 on and off, a zener diode 306 which is rendered conductive when the potential at the second rectifier output terminal 202 reaches the first preset voltage value, a pair of resistors 307, 308 connected in series and serving as a voltage divider, and an initial exciting resistor 309 connected in parallel to a charging indicator lamp 6 and capable of supplying an initial exciting current to the generator even when the charging indicator lamp 6 is disconnected. A storage battery 4 is connected to the full-wave rectifier 2 and also to the voltage regulator 3 through a key-operated switch 5.
The operation of the control apparatus thus constructed is as follows: When the key-operated switch 5 is closed to start the engine, a base current flows from the storage battery 4 through the key-operated switch 5 and the resistor 304 to the transistors 302, 303 which are rendered conductive. When the transistors 302, 303 are energized, a field current flows from the storage battery 4 through the key-operated switch 5, the charging indicator lamp 6, the resistor 309, the field coil 102, and the transistors 302, 303 to enable the field coil 102 to generate a field magnetomotive force. When the engine is started at this time, the generator 1 is driven and an a.c. output is induced in the armature coils 101 dependent on the RPM of the engine. The induced a.c. output is rectified by the full-wave rectifier 2. If the rectified output is lower than the first preset value, the zener diode 306 remains non-conductive as the potential at the voltage dividing point of the voltage divider resistors 307, 308 is low. Accordingly, field current continues to be supplied to the field coil 102, and the output voltage from the generator 1 increases as the RPM thereof increases. When the output voltage from the generator 1 exceeds the first preset value, the potential at the voltage dividing point of the voltage divider becomes high to the point where the zener diode 306 is rendered conductive, wherein a base current is supplied to the transistor 305 which is then made conductive. Upon energization of the transistor 305, the transistors 302, 303 are de-energized to cut off the current flowing through the field coil 102. The output voltage from the generator 1 now begins to drop. When the output voltage from the generator 1 becomes lower than the first preset value, the zener diode 306 and the transistor 305 are turned off, and the transistors 302, 303 are again turned on to energize the field coil 102. The output voltage of the generator 1 is thus increased once again.
The above cycle of operation will be repeated to control the output voltage of the generator 1 to the first preset value for charging the storage battery 4 at such controlled voltage. At this time, the output voltage at the second rectifier output terminal 202 is substantially equalized with the first preset value. Since there is now almost no potential difference between the second rectifier output terminal 202 and the storage battery 4, the charging indicator lamp 6 is turned off indicating the storage battery 4 has been charged.
In the event of disconnection of a portion of the exciting circuit, however, the charging indicator lamp 6 may remain de-energized even with the generator 1 not being operated. Accordingly, should this happen, the user could not recognize the fact that the storage battery 4 was not being charged, allowing the storage battery 4 to be discharged, and would similarly be unable to identify a disconnection of the first rectifier output terminal 201 or an uncontrolled output voltage.